1. Field of the Invention
The present invention relates generally to a dog clutch transmission for a marine vessel and, more particularly, to a marine transmission which incorporates both friction and dog clutch mechanisms in cooperation with hydraulic actuators that at least partially synchronize the rotational speed of a driving shaft and a driven shaft prior to engagement of the dog clutch elements.
2. Description of the Prior Art
Dog clutches of various types are well known to those skilled in the art and are used in many different variations of marine transmissions.
U.S. Pat. No. 1,931,288 which was granted to Griswold on Oct. 17, 1933, describes a transmission with an improved device for synchronizing the gear elements and in which the operation of the synchronizing clutches are affected through rotating parts not subjected to high relative speeds.
U.S. Pat. No. 2,091,557, which was granted to Montgomery on Aug. 31, 1937, describes a marine power transmission with a clutch housing located between an engine and the transom of a marine vessel. This application is intended to adapt high speed automotive or industrial-type engines to marine use.
U.S. Pat. No. 3,563,354, which issued to Sigg on Feb. 16, 1971, describes an automatically engaging and disengaging dog clutch. The dog clutch is disposed between an input shaft and an output shaft and includes a first straight-toothed clutch boss, a second helical-tooth clutch boss, an axially slidable clutch spider and a synchronizing sleeve which is retained against axial movement in the clutch spider.
U.S. Pat. No. 3,919,964, which issued to Hagen on Nov. 18, 1975, describes a marine propulsion reversing transmission with a hydraulic assist. The transmission is located in a propulsion unit and connected to a drive shaft and to a propeller shaft. It is shiftable between neutral, forward drive, and rearward drive conditions.
U.S. Pat. No. 4,349,091, which issued to Miyake et al. on Sep. 14, 1982, describes a synchronized dog clutch. It comprises a clutch shaft, a coupling sleeve splined to the clutch shaft and dog claws at its end. A synchronizer ring is slidably fitted to the outer periphery of the coupling sleeve and has a conical face for friction engagement.
U.S. Pat. No. 4,811,825, which issued to Christian et al. on Mar. 14, 1989, describes a dog clutch with locking synchronization. A synchronizer body and a gear turning with a different rotational speed are coupled together with the aid of an axially displaceable, annularly shaped sliding sleeve when synchronized.
U.S. Pat. No. 5,170,872, which issued to Salicini on Dec. 15, 1992, describes a synchronizer for activating and deactivating a dog clutch, particularly in article wrapping machines. The outputs of a pair of intermittence devices operated in phase with a clutch driving shaft is described. Electromagnetic friction clutches allow outputs to be connected to the driven disc of the clutch.
U.S. Pat. No. 6,062,360, which issued to Shields on May 16, 2000, discloses a synchronizer for a gear shift mechanism for a marine propulsion system. A synchronized gear shift mechanism is provided for a marine propulsion system. Using a hub and a sleeve that are axially movable relative to an output shaft but rotationally fixed to the shaft and to each other, the gear shift mechanism uses associated friction surfaces to bring the output shaft up to a speed that is in synchronism with the selected forward or reverse gear prior to mating associated gear tooth surfaces together to transmit torque from an input shaft to an output shaft. The friction surfaces on the forward and reverse gears can be replaced to facilitate repair after the friction surfaces experience wear.
U.S. Pat. No. 6,460,425, which issued Bowen on Oct. 8, 2002, describes a twin clutch automated transmission. The transmission includes a first engine clutch operable to establish a releasable drive connection between the engine and a first input shaft, a second engine clutch operable to establish a releasable drive connection between the engine and a second input shaft, an output shaft and a gear trained for selectively establishing a plurality of forward and reverse speed ratio drive connections between the input shafts and the output shaft.
U.S. Pat. No. 6,672,180, which issued to Forsyth on Jan. 6, 2004, describes a manual transmission with upshift and downshift synchronization clutches. An automated multi-speed transmission includes an engine clutch operable to establish a releasable drive connection between the engine and an input shaft, an output shaft adapted to transfer power to the drive line, and a synchromesh gear train having a plurality of constant mesh gear sets that can be selectively engaged to establish a plurality of forward and reverse speed ratios.
U.S. Pat. No. 6,571,654, which issued to Forsyth on Jun. 3, 2003, describes an automated manual transmission with upshift ball ramp synchronizer clutch and downshift ball ramp synchronizer clutch. The transmission includes an engine clutch operable to establish a releasable drive connection between the engine and an input shaft, an output shaft adapted to transfer power to the drive line, and a synchromesh gear train having a plurality of constant mesh gear sets that can be selectively engaged to establish a plurality of forward and reverse gear speed ratios.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
In marine transmissions, dog clutches are commonly used to connect a driving shaft to a driven shaft in either a forward or reverse direction. It would be helpful and beneficial if a marine transmission could provide a means for diminishing the impact during initial contact between dog clutch surfaces that creates a noise when the transmission is shifted from neutral to either forward or reverse gears.